The present invention relates to an electromagnetic shuttle valve as it is commonly used in electro-hydraulic brake systems that are equipped with traction control or electronic stability control functions. This valve is located between the suction side of a self-priming hydraulic pump and the brake line which through a non-actuated master cylinder is connected to the brake fluid reservoir. The shuttle valve has the purpose to connect the suction side of the pump to the brake line if brake fluid needs to be supplied to the pump from the reservoir. Otherwise, it remains in its normally closed position.
A shuttle valve of this kind is for instance known from the German published patent application DE 10252231 A1. The valve includes a first and second valve passage controlled by a first and second valve closure member, with the second valve closure member is integrated into the same part that carries the first valve piece. In this coaxial arrangement, the second valve passage can only be opened when the first valve passage is open. The first valve passage is formed by an orifice, while the second valve passage ideally has a large fluid flow cross-section. The first valve closure member is biased toward the first valve seat by a compression spring and is removed from the first valve seat by means of the excitation of an electromagnetic coil. The second valve closure member, which is manufactured in one piece with the first valve seat, is biased toward the first valve closure member by means of the compression spring and can only move away from the second valve seat if the first valve closure member has been removed from the first valve seat. The compression spring acting on the second valve closure member is arranged around the circumference of the second valve closure member. This limits the available diameter of the second valve closure member and thus of the second valve passage. However, in cold temperatures when the brake fluid is highly viscous, a larger diameter for the second valve passage is desirable.
It is therefore the objective of the current invention to suggest a valve design that allows for a larger cross-section of the second valve passage.
It is another objective of the current invention to keep the cost of the valve low without complicating manufacturing.